All water under the bridge now. Especially as Triple H is getting more and more power behind the scenes, basically going to succeed Vince when he retires/dies. X-Pac had a drug problem a few years ago and Triple H sorted him out, getting him into rehab. Gunn was just bitter that he got released as a wrestler in 2004, but now he's employed by WWE again.
Triple H runs NXT and developmental now, almost exclusively without Vince's involvement. Triple H is the one hiring new talent & employees. Gunn got hired a month or two ago to work as a trainer with the new talent in NXT, hence why he's wearing a shirt & tie in that video/photo. Running NXT is basically Triple H's practice for when he's running the whole company when Vince is gone.